Transformer with variable magnetic shunt



July 12, 1949.

Filed Oct. 9, 1944 e. G. LANDIS 2,475,623

TRANSFORMER WITHVARIABLE MAGNETIC SHUNT 2 Sheets-Sheet 1 I N VEN TOR.

I GEORGE G. LANDIS BY 619.? ii

ATTORNEYS July 12, 1949. sis. LANDIS TRANSFORMER WITH VARIABLE MAGNETIC SHUNT Filed Oct. 9, 1944 2 Sheets-Sheet 2 r1 mEESSESHI INVENTOR. 47 GEORGE s. LANDIS ATTORNEYS Patented July 12, 1949 2,475,623 TRANSFORMER WITH VARIABLE MAGNETIC SHUNT George G. Landis, South Euclid, Ohio, assignor to The Lincoln Electric Company, Cleveland, Ohio, a corporation of Ohio Application October 9, 1944, Serial No. 557,766

Claims. (Cl. 171--119) The present improvements relate to the regulation of induction voltage, and more particularly to the regulation of the current or potential in a transformer secondary. Still more particularly the invention relates to improvements in a transformer or equivalent apparatus for supplying A. C. current to an arc welding circuit.

In U. S. Letters Patent No. 2,299,329, issued to me under date of October 20, 1942, there is disclosed a construction of close-coupled transformer wherein the primary and secondary coils are separated at a point within the contour of the main magnetic circuit and a variable magnetic bridge is provided in the area of separation of said windings. In the specific construction illustrated in said patent this bridge takes the form of a rotor of magnetic material suitably mounted within the stator of the transformer and means are provided whereby such rotor may be set to occupy various positions about its axis and thus correspondingly vary the current flow in the secondary coil of the transformer, or in other words the character of the current delivered to the secondary circuit, which in an arc welding system will of course be the main welding circuit.

I have now discovered that, particularly where employed in arc welding, such variable magnetic bridge in a transformer of the construction in question will desirably be constructed so .as to have a capacity for limited amplitude of free movement subject to suitable controls whereby the current in the secondary or welding circuit may be automatically varied to meet conditions encountered in the operation of arc welding with an A. C. current. A particular object of such improvement is to permit striking the are with the short-circuit impedance set at an adjustable predetermined amount below normal and then automatically increasing such impedance to its normal value after the arc is established.

Use of the improvements in question is not necessarily limited to such particular construction of transformer in which the primary and secondary coils are arranged as above stated, but may be advantageously employed with other types of transformers and indeed such improvements may be employed in connection with reactan'ce coils or like devices interposed in an A. C. Welding circuit, wherein it is desired to regulated the current in the manner just stated or in other analogous ways.

To the accomplishment of the foregoing and related ends, said invention. then, consists of the 2 means hereinafter fully described and particularly pointed out in the claims.

The annexed drawings and the following description set forth in detail certain mechanism embodying the invention, such disclosed means constituting, however, but one of various mechanical forms in which the principle of the invention may be used.

In said annexed drawings:

Fig. 1 is a central section through one form of transformer in which my present improvements have been incorporated;

Fig. 2 is a transverse horizontal sectional view thereof taken on the plane indicated by the line 2-2 Fig. l;

Fig. 3 is similarly a transverse horizontal section taken on the plane indicated by the line 2-2 Fig. 1, certain of the superposed parts being shown in dotted outline and other parts being shown in different operative position;

Fig. 4 is a top plan view of another form of transformer embodying my present improvements;

Fig. 5 is a central vertical section of the sam taken on the plane indicated by the line 5-! Fig. 4.

Fig. 6 is a wiring diagram showing the manner in which either of the aforesaid transformers may be included in an A. C. welding circuit; and

Fig. 7 is a view, similar to Fig. 3, showing the present improvements as incorporated in a reactor instead of a transformer.

Referring to the construction of transformer illustrated in Figs. '1, 2 and 3; such construction will be seen to follow closelyin certain respects that which formed the subject matter of my above-identified Patent No. 2,299,329.

. Thus the parts of the transformer are enclosed in a domed shell I mounted on a cylindrical base 2 which may, if desired, be in turn supported on suitable feet (not shown). The main elements of the transformer comprise a laminated stator 5 of general hollow cylindrical shape, two pairs of coils 6 and I which pass around and are supported by such stator, and a rotatable magnetic bridge 8 mounted in a cylindrical space at the center of the stator, said bridge or rotor being carried by a spindle 9. The individual plates or blanks l0 whereof the laminated stator is constructed are are shaped in form, the centers of such plates being stamped out to leave an inwardly directed arcuate portion 1!, the inner edge of which is formed on a circle having a diameter slightly larger than the rotor 8 and being formed, on each side with a curved recess [2.

rotatable member 8 constitutes a magnetic bridge between said projections.

In the specific construction of the transformer as illustrated and described in my above-identified patent, rotor 8 is provided with suitable handled means whereby it can be moved into different rotative positions about its axis so as to provide a variable magnetic bridge between the opposite portions of the stator, constituted by the projections ll thereof. In order to indicate the particular setting of a rotor, as adjusted by such handled means, a radially projecting indicating pointer I3 is mounted as before on the upper end of the rotor, the outer end of such pointer extending through an arcuate slot in the housing i so as to move along an arcuate plate l4 marked with suitable indicia.

In the present improved construction, instead of providing handled means as aforesaid whereby the rotor can be set in adjusted position about its axis, such rotor is left free to rotate withinpredetermined adjustable limits, such movement, however, being under controlled conditions as will now be set forth. As will also be explained, the present improved construction instead of displacing such handled adjustment for the rotor may be employed alternatively with the latter, i. c. said rotor may be either adjusted manually as before or operated in accordance with the present invention, as occasion may require.

Extending radially from the lower end of spindle 9 which carries the rotor 8 is an arm it the outer end of which is movable over an arcuate slotted traclr iii. In the slot of such track, or otherwise adjustably secured thereto, are stops ii and it; which limit the oscillatory movement of the arm and thus of the rotor. When moved to their extreme outer positions these stops will permit movement of the rotor through an angle of approximately 90, i. e. from the position shown in Fig. 2 to that shown in Fig. 3, the first of these being what may be termed the normal position of the rotor, to which it is moved, when not otherwise influenced, by the action of a tension spring is connected at one end to the arm 15 and at the other end to a fixed point in the housing.

Rotatably supported in a suitable bearing 20 below the lower end of spindle 9 and coaxial therewith is a fan 2i that is connected through an over-running clutch 22 with such lower spindle end. This clutch, which may be of any familiar type of construction, is so arranged that when the spindle, and thus the rotor, moves in -clockwise direction, the fan will be coupled to the spindle and caused to rotate therewith. However, at the end of such rotative movement of the spindle, or upon reverse movement thereof, 1. e. in a counterclockwise direction, the fan is entirely disengaged from the spindle. The normal position of the rotor, as illustrated in Fig. 2, is that which it occupies when no current is flowing through the transformer secondaries or, in other words, when the secondary circuit is interrupted. Actually, in such normal position, the rotor will lie slightly oil the shown in said figure to insure its turning in the desired direction when the flux path is established between the opposite projecting portions of the stator. Upon the closing of such circuit. with resultant flow of current through the secondary coils of the transformer, the magnetic field set up will cause rotation. of the rotor from such normal position to that shown in Fig. 3. It will be understood that by shifting the adjustable stops I! and I8 the two positions which the rotor may thus assume may be varied from those shown in Figs. 2 and 3; thus in such normal position instead of being entirely clear of the projections H, as shown in the first of these figures, it may be retained partially within such projections, and similarly it may be held from swinging into complete alignment with such projections, as shown in the second of these figures.

Movement of the rotor from the position shown in Fig. 2 to that shown in Fig. 3 will, as prevlously described, involve picking up the fan member 2| through the over-running clutch 22. Due to the inertia of the fan, the effect of such engagement will be to retard movement of the rotor from the one position to the other so that its final adjusted position between the projections ll of the stator will be assumed only after a predetermined time interval. However, when the rotor is left free to return to its normal position, as by breaking the secondary circuit and thus interrupting the magnetic field in the transformer, the rotor moves unhindered by any connection with the fan.

Where, as in an arc welding operation, the arc and thus the secondary circuit of the transformer is interrupted frequently, the rotative movement of the fan may produce a suflicient current of air through the transformer to have an appreciable and desirable cooling effect.

As previously indicated, if instead of leaving the rotor free to move about its axis between the limits defined by the adjustable stops i'i and it it should be found desirable to utilize the transformer in the manner set forth in my pre vious Patent No. 2,299,329, the same means for adjusting the position of the rotor within the stator and for maintaining the same in such adjusted position may be utilized with a slight modification only. To this end a handle 23 may be provided as before, which upon being manually depressed releases a friction retaining device 24 and permits the rotor to be turned about its axis. It is deemed unnecessary to describe the details of such retaining device since they are substantially identical with those shown in the above-identified patent. However, since in using the apparatus in the manner hereinabove set forth, the rotor requires to be left free to turn under the influence of the magnetic field, the spring 24a which normally actuates friction retaining device 24 is adapted also to retain said handle 23 in depressed position, where it is inoperative. It will be understood of course that when the device is to be operated through the medium of said handle in order to set the rotor in desired position and leave it in such set position, the stops I1 and 3 will be moved to the respective ends of the slotted track is So as to allow such setting of the rotor at any point within its full range of turning movement.

The modified construction of transformer illustrated in Figs. 4 and 5 is disclosed in my copending application flled September 8, 1943, Serial No. 501,589, and now abandoned, from which claims to such construction have been required to be divided out. Such modification, which embodies the same principle of operation as does the previously described construction of transformer, includes a stator of magnetic material and primary windings 26, 28 and secondary windings 21, 2'! arranged thereon in much the same fashion as in the case of the first described construction of transformer. In particular. such primary and secondary windings, as best shown in Fig. 4, are located closely adjacent to each other throughout the major portion of their extent, but are substantially separated where they pass through the hollow interior portion of the stator. Movably interposed within such portion, i. e. in the area of separation of the transformer windings, is amagnetic bridge or core 28 which is reciprocable axially of the stator bore. In order to permit oi? such movement such core is conveniently mounted on a rod or spindle 29 guided in suitable bushings 30 and 30' provided in the top and bottom walls respectively of the casing 3| in which the body of the transformer is housed.

In the specific construction illustrated, the axis of the stator bore is designed to be vertically disposed and the core 28 will accordingly normally tend under the influence of gravity to drop downwardly entirely clear of such bore. Such downward movement is substantially free. but upward movement is retarded by means of a dash pot 32 secured to the lower wall of the housing by means of a supplemental housing 33, the piston 34 -01 such dash pot having a valve 35 that restricts the rate of flow of the fluid, such as oil, with which the dash pot is filled, during the upward movement of the piston and thus of the core 28.

While the downward movement of the core 223 is free, as just stated, the extent of such movement is adapted to be adjustably limited by means of a stop 36 on the lower end of a screw 3? rotatably mounted in a supplemental housing St on. the upper wall of the main transformer housing.

a handle 38 on the upper end of the screw faciii tates rotation of the latter so as to raise or lower such stop, and an arm dd fixed to the upper end of the rod or spindle 29 which" carries core 28 has an aperture which fits over the screw, and by engagement with the stop on the lower end there of will retain the core against further downward movement.

Adjustable means are also provided to limit the upward movement of the core, such means comprising a second handled rod 422 similarly threaded in the aforesaid supplemental housing in alignment with the end of the rod or spindle 2i).

Normally the core 28 will occupy its lowermost position as determined by the position of adjustable stop 36. Thus such core may lie entirely without the stator bore or extend partially upwardly within the same. This will be the position of the parts when no current is flowing through the transformer secondaries, or in other movement, so that the full operating position in iii) question will be assumed only after a predetermined time interval. Furthermore, by adjusting the stop carried by screw 42, the core can be prevented from coming fully in line with the stator if desired.

For the purpose of illustrating one field of use for a transformer in which the current or potential in the secondary circuit'is regulated in the manner hereinbefore set forth, there is shown in Fig. 6 a welding circuit in whicha transformer of the construction illustrated in Figs. 4 and 5 constitutes the source of current supply. In said Fig. 6 the primary windings 26, 26, shown in conventional manner, are connected in series'to the alternator A5 or other suitable source of alternating current, which will deliver current at desired voltage or frequency; while the secondary windings 2'1, 21 are connected in series with the welding electrode 48 and the work-piece it between which the arc is struck during the welding operation. At the start of such operation the core 28 will occupy its lowermost position as previously described, but immediately the arc is struck the flow of current through the trans former will tend to lift the core to bring it in line with the stator bore. the dash pot sii'retards the foregoing movement so as to take from a fraction of a second up to several seconds, the return movement of the core following interruption oi the arc and of the current flowing through the transformer, will be unimpeded by the dash pot and so b practically instantaneous? V g Where a transformer of the construction illus trated in Figs. 1, 2 and 3 is used in a welding circuit such as just described, the connections will be identically the same and the manner in which the rotary cor or magnetic bridge operates will likewise correspond with that of the reciprocable core in the form of apparatus last referred to.

The principle of the invention may also be used in forms of electrical apparatus other than a transformer, one such modification being shown in Fig. 7, which illustrates a reactor designed for inclusion in an A. C. welding circuit. As thus shown, said reactor comprises a hollow stator body 5 similar to that employed in the first form of transformer illustrated in Figs. 1, 2 and However, in place of primary and secondary coils, said stator is provided with two reactance coiis t?) and lticonnected in series, said coils being wound about the respective inwardly directed projections ii, iii of the stator. Suitable leads, not shown, respectively connect these reactance coils with any suitable source of A. 0. current and with the welding electrode, the work-piece being similarly connected by another lead with such source.

A rotatable bridge identical with the one employed with such first described form oi appa ratus, having the same capacity oi movement and such movement being controlled in identi cally the same way, is utilized in this modified apparatus, the corresponding part-s bearing the same reference numerals as in Figs. 1, 2 and 3. The operative efiect of said bridge member wiil be to control the flux path of the reactor provided by said coils 45, 46, just as such bridge in the previous construction serves to control the flux path of the transformer windings.

Other modes of applying the principle of my invention may be employed instead ,of the one explained, change being made as regards the mechanism herein disclosed, provided the means While the action oi stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

1. The combination with an electric transformer comprising a stator and primary and secondary coils arranged on said stator whereby a flux path is formed between opposite portions thereof, of a movable magnetic bridge in such flux path, said bridge being movable in one direction under the influence of such field, manual means for moving said bridge, means normally holding said manual means inoperative, and time-delay means controlling movement of said bridge under the influence of such field.

2. In apparatus of the character described, a stator and primary and secondary windings associated therewith closely coupled in part and loosely coupled in a local area, whereby a flux path is formed between opposite portions of said stator, of a movable magnetic bridge in such path, said bridge being movable in one direction under the influence of such flux, manual means for moving said bridge, means normally holding said manual means inoperative, and time delay means controllin such movement.

3. In apparatus of the character described, a stator and primary and secondary windings associated therewith closely coupled in part and loosely coupled in a local area, whereby a flux path is formed between opposite portions of said stator, of a movable magnetic bridge in such path, said bridge being movable in one direction under the influence of such flux, manual means for moving said bridge, means normally holding said manual means inoperative, and time delay means controlling such movement, said bridge being freely movable in the opposite direction.

4. In apparatus of the character described, a stator and primary and secondary windings associated therewith closely coupled in part and loosely coupled in a local area, whereby a flux path is formed between opposite portions of said stator, of a movable magnetic bridge in such path, said bridge being movable in one direction under the influence of such flux, manual means for moving said bridge, means normally holding said manual means inoperative, and time delay means controlling such movement, said bridge being freely movable in the opposite direction, and adjustable means adapted to limit the movement of said bridge in each such direction.

5. In a transformer comprising a stator and primary and secondary windings arranged thereon, said windings being thus arranged closely to each other, as in a closely coupled transformer throughout the major portion of their extent and being substantially separated, as in a loosely coupled transformer in a local area, of a movable magnetic bridge disposed between opposite portions of said stator in the area of separation of said windings, said bridge being movable in one direction under the influence of the magnetic field set up by said transformer, manual means for moving said bridge, means normally holding the latter means inoperative, and time delay means controlling such movement.

6. In a transformer comprising a stator and primary and secondary windings arranged thereon, said windings being thus arranged closely to each other, as in a closely coupled transformer throughout the major portion of their extent and being substantially separated, as in a loosely coupled transformer in a local area, of a movable magnetic bridge disposed between opposite portions of said stator in the area of separation of said windings, said bridge being movable in one direction under the influence of the magnetic field set up by said transformer, manual means for moving said bridge, means normally holding the latter means inoperative, and time delay means controlling such movement, said bridge being freely movable in the opposite direction.

'7. In a transformer comprising a stator and primary and secondary windings arranged thereon, said windings being thus arranged closely to each other, as in a closely coupled transformer throughout the major portion of their extent and being substantially separated, as in a loosely coupled transformer in a local area, of a movable magnetic bridge disposed between opposite portions of said stator in the area of separation of said windings, said bridge being movable in one direction under the influence of the magnetic field set up by said transformer, manual means for moving said bridge, means normally holding the latter means inoperative, time delay means controlling such movement, said bridge being freely movable in the opposite direction, and adjustable means adapted to limit the movement of said bridge in each such direction.

8. In a transformer comprising a stator and primary and secondary windings arranged thereon, said windings being thus arranged closely to each other, as in a closely coupled transformer throughout the major portion of their extent and being substantially separated, as in a loosely coupled transformer in a local area, of a rotatable bridge disposed between opposite portions of said stator in the area of separation of said windings, said bridge being movable in one direction under the influence of the magnetic field set up by said transformer, manual means for moving said bridge, manually releasable clutch means normally holding the latter means inoperative, and time delay means controlling such movement.

9. In a transformer comprising a stator and primary and secondary windings arranged thereon, said windings being thus arranged closely to each other, as in a closely coupled transformer throughout the major portion of their extent and being substantially separated, as in a loosely coupled transformer in a local area, of a rotatable bridge disposed between opposite portions of said stator in the area of separation of said windings, said bridge being movable in one direction under the influence of the magnetic field set up by said transformer, manual means for moving said bridge, manually releasable clutch means normally holding the latter means inoperative, time delay means controlling such movement, and a spring tending to move said bridge in the opposite direction,

10. In a transformer comprising a stator and primary and secondary windings arranged thereon, said windings being thus arranged closely to each other, as in a closely coupled transformer throughout the major portion of their extent and being substantially separated, as in a loosely coupled transformer in a local area, of a rotatable bridge disposed between opposite portions of said stator in the area of separation of said windings, said bridge being movable in one direction under the influence of the magnetic field set up by said transformer, time delay means controlling such movement, a spring tending to move said bridge in the opposite direction, manual means for moving said bridge, manually releasable clutch means normally holding the latter means inoperative, and adjustable means adapted to 10 limit the movement of said bridge i n each such UNITED STATES PATENTS direction.

GEORGE G. LANDIS. Number Name Date 735,103 Hull Aug. 4, 1903 REFERENCES CITED 5 991,108 Turbayne May 2, 1911 2,299,329 Landis Oct. 20, 1942 The following references are of record in the file of this patept: 

